The invention relates generally to closures for containers and more specifically to closures having a plug or valve style liner.
Packages for poisons, chemicals and medications used both commercially and in the home typically include closures which require a certain degree of manual dexterity for their removal. Such dexterity is typically not exhibited by infants and those of similar intelligence who might not appreciate the possible dangers of the product contained therein. Furthermore, it is desirable that the closure be readily replaced on the container with simple, conventional movements known to all so that such replacement is encouraged in order to resecure the contents from accidental use.
Numerous types and designs of safety caps and cooperating container configurations are disclosed in the prior art. A significant distinction or means of grouping such configurations addresses whether the closure must provide a fluid tight seal in cases where the container will hold a liquid or simply close the container and provide a nominal seal to prevent discharge of pills, capsules, powders and the ingestion of foreign material.
Those devices constituting the first group have been the subject of much development effort which is well documented in the patent literature. For example, U.S. Pat. Nos. 3,830,391 to Uhlig, 3,941,268 to Owens et al. and 4,134,513 to Mumford are representative of such art. These patents are directed to various embodiments of closures which typically include a pair of opposed webs or lugs which coact with a pair of stepped, camming surfaces suitably disposed about the neck of the container. In order to remove the closure from the container, the closure must be squeezed at locations substantially intermediate the opposed lugs to increase the diameter of the cap adjacent the lugs. When the closure is rotated, the lugs clear the steps of the camming surfaces and permit removal of the closure from the container. Typically, the lugs and camming surfaces will extend and interfere over a certain axial distance so that the closure must be gripped and squeezed at least twice, an action which requires a certain amount of intelligence, dexterity and intent on behalf of the user. This cap design also satisfies requirements for quick and simplified resecurement to the container inasmuch as only conventional circular motion is required; the lugs now simply riding the camming surfaces without interfering with rotation of the closure.
Clearly such safety closures and related designs are somewhat more complex than conventional closures. The complexity of molds for such closures not only renders them expensive but frequently limits the particular material which may be utilized therein to fabricate the closure. These considerations become significant when it is appreciated that each distinct container configuration requires a distinct closure and thus mold, and that the limitation on material use may create difficulties if the only materials capable of being utilized in a given mold to fabricate a given closure are incompatible with, i.e., may be attacked by, the product which is to be placed in the subject container. Such difficulties suggest the utilization of a liner disposed within the closure structure, which is fabricated of material distinct from that of the closure proper. A closure having a liner is generally illustrated in U.S. Pat. No. 3,247,992.
As those familiar with closures which incorporate cooperating lugs and camming surfaces will appreciate, it is often possible to rotate the closure substantially but less than one-half turn before the lugs and steps of the camming surfaces engage and inhibit further rotation and removal of the closure. If the contents of the container is a liquid, such rotation may cause sufficient axial traverse of the closure to allow the liquid to escape. Depending upon the character of the liquid, this may or may not create difficulties. Nonetheless, it is often desirable to preclude such leakage. The previously referenced U.S. Pat. No. 4,134,513 discloses a plug style closure which provides a seal over a substantial portion of the rotation and thus axial traverse of the closure on the container finish.